(clone-init-mode-variables): Don't defvar

(clone-init-mode-variables): Don't defvar
variables if already bound.  Put on clone-unmerged props if
they were not bound.
(clone-make-docstring): Install the map unconditionally;
set clone-unmerged property to nil.  No clone-merged property.
(clone-set-syntax-table): Set clone-unmerged prop, not clone-merged.
(clone-set-abbrev-table): Call clone-merge-abbrev-tables.
Don't touch properties here.
(clone-merge-keymaps): Splice out the `keymap' of the OLD map.
(clone-merge-abbrev-tables): New function.